This has happened to several of my students in the last day--I would say about 20% of the students have tried to sign in so far. The only way the first student was able to access our class blog (which is private) was to completely create a new username and re-register, and then I sent her a new invitation to her new username. Now that this is happening to about 15 other students, I hesitate to make this the default solution...

@tbalandry
re: One of our users
Please post the username for Staff. I'll tag this thread for their assistance. Please subscribe to the thread so you are notified when they respond and please be patient while waiting.

Hi! Thanks for your swift reply. I've put the URLs of my 3 class blogs and the usernames of students who are having trouble for each blog. I initially sent them each an invitation (to be 'authors') on our private class blog. It seems when some of them are initially registering they can't get access to our blog. So they are sending a request for access (which comes to my email from WordPress). I tried clicking on the link in this message, but I realize now that this merely makes them viewers, not authors.

This is a typical message from a student about their experience: "I set up my wordpress username but when I click on "accept invitation" a screen pops up saying that I can't log in because of security reasons or because my session timed out. Is there another way to join the blog?"

The second URL is http://ideasandideologies2.wordpress.com/
For this blog, the following usernames have had trouble so far:
hmontgo1
jsimons504
radicalradigan
patriciaherrmann
ltomaro
jcampbe4
mobrien42013

Hmm... the 'fix' above only seems to be helping some students. Others are still getting the error. At this point the list of usernames above is out of date. Some have been able to access it, more have not.

@kdietz If all the students register for WordPress.com accounts or accepting an invitation at the same time from the same classroom, it might trigger our anti-spam system, because it looks just like an automated spam attack.

A great way to get around that is to make signing up at WordPress.com their first homework assignment.